No Retrograding, moving forward.

CHAPTER 6
Heb 6:1-14. Warning against Retrograding, Which Soon Leads to Apostasy; Encouragement to Steadfastness from God's Faithfulness to His Word and Oath.
1. Therefore—Wherefore: seeing that ye ought not now to be still "babes" (Heb 5:11-14).
leaving—getting further forward than the elementary "principles." "As in building a house one must never leave the foundation: yet to be always laboring in 'laying the foundation' would be ridiculous" [Calvin].
the principles of the doctrine—Greek, "the word of the beginning," that is, the discussion of the "first principles of Christianity (Heb 5:12).
let us go on—Greek, "let us be borne forward," or "bear ourselves forward"; implying active exertion: press on. Paul, in teaching, here classifies himself with the Hebrew readers, or (as they ought to be) learners, and says, Let us together press forward.
perfection—the matured knowledge of those who are "of full age" (Heb 5:14) in Christian attainments.
foundation of—that is, consisting in "repentance."
repentance from dead works—namely, not springing from the vital principle of faith and love toward God, and so counted, like their doer, dead before God.

This repentance from dead works is therefore paired with "faith toward God." The three pairs of truths enumerated are designedly such as Jewish believers might in some degree have known from the Old Testament, but had been taught more clearly when they became Christians.

This accounts for the omission of distinct specification of some essential first principle of Christian truth. Hence, too, he mentions "faith toward God," and not explicitly faith toward Christ (though of course included). Repentance and faith were the first principles taught under the Gospel.